Blister Agents

Introduction

Blister Agents or vesicants are chemicals which have severely irritating properties and can produce irritated and reddened skin with progression to
blisters, swelling and inflammation of tissues surrounding the eyes with progression to light sensitivity and lacrimation. High concentrations of vapor or direct liquid exposures
to the eye can cause damage to the eye surface. Warm, moist tissues are most susceptible to damage and the tissues of the upper respiratory tract can also be affected. Symptoms
of exposure may be delayed until hours or days after exposure depending on the magnitude of the absorbed dose. The major chemical warfare agents in this category are
sulfur mustard, nitrogen mustard and Lewisite.

Personal Protective Equipment

The recommendations for personal protective equipment (PPE) should be based on a site-based job hazard analysis of possible hazards including skin contact, air concentrations, heat stress, etc. All PPE should be used with appropriate additional administrative controls including medical surveillance, employee training, respirator fit-testing, and decontamination procedures to limit the potential for unforeseen adverse effects.

There are no current OSHA Permissible Exposure Limits (PELs) for exposure to blister agents. The National Research Council and EPA have published airborne limits to various
agents called
Acute Exposure Guideline Levels (AEGLs) to characterize the risk to the general population during a one-time accident and emergency scenario with time limits not to exceed 8
hours of exposure. For emergency responders and support personnel to a blister agent event, it seems appropriate to establish a target exposure limit at time weighted
averages less than the lowest recommended AEGL-1 level for a given exposure duration. The AEGL-1 tier is the mildest effect category above which the general population,
including susceptible individuals, could experience noticeable eye discomfort, irritation, or non-sensory effects. However, the effects are not disabling and are reversible upon
cessation of exposure. The AEGL-1 and AEGL-2 values are based upon direct vapor exposure to the human eye and tissues surround the eye (conjunctiva), which are considered the
most sensitive organ/tissue for blister agent vapor exposure effects by the National Research Council and the National Academy of Sciences. The CDC has made recommendations for
worker exposure limits dealing with routine work processes such as
demilitarization and transportation. Note: The CDC/NCEH worker exposure limits do not specifically include storage. These exposure standards may be substituted for work extending
beyond the 8-hour AEGL limit if deemed appropriate after an incident.

The PPE ensemble selected depends on the level of knowledge available regarding the chemical agent. Respirators chosen initially for responders into a known release area
should be a positive pressure self-contained breathing apparatus (SCBA) with a Level A protective suit until monitoring results allow for other decisions. OSHA
would generally require these respirators to be NIOSH-certified CBRN SCBA respirators for use by employees. Some chemical warfare agents have been shown to seriously degrade and damage some respirators. Respiratory protection specifically approved by NIOSH for CBRN exposures is highly desirable but where not available, the incident commander may allow alternative suitable respirators during emergency operations. These are, depending on exposure levels, other NIOSH approved SCBAs or full-face air purifying respirators, which have been specifically tested by the manufacturer as effective against chemical warfare agents. Respirators other than SCBAs may be selected based upon accurate monitoring results with appropriate limits of detection for the subject agent. When conditions have been determined to be appropriate for the use of air purifying respirators, a NIOSH-approved CBRN APR Full Facepiece Air Purifying Respirator (APR) with a CBRN Canister, or a Chemical Warfare Agents (CWA) tested full
facepiece APR with a combination organic vapor/acid gas/particulate canister may be used. A list of CBRN approved SCBA and APR may be obtained from the NIOSH website - APR or SCBA.

The requirements for skin protection from above the AEGL-1 but below the AEGL-2 should be focused initially on reducing the potential for contact with liquid agent residue. As
airborne exposure rises above the AEGL-2 level, the potential for significant vapor absorption through the skin is possible and exposed skin should be minimized with the use of
chemically protective clothing, preferably vapor tight encapsulating suits. Above AEGL-3, the incidence and severity of skin burns will increase and the use of encapsulating
suits should be mandatory.

The tables below consolidate some information relating to AEGL exposure levels and the relative protection provided by certain types of respirators and clothing. These
limits are for planning purposes and are not recommendations for particular work schedules. Any work schedules should be reviewed by a competent occupational health
professional skilled in use of exposure limits and PPE. All air purifying respirators require a change schedule for cartridges or canisters not to exceed the maximum
eight-hour exposure covered by the AEGLs.

Respiratory: Any NIOSH CBRN-approved or CWA tested SCBA or a NIOSH-approved CBRN APR Full Facepiece Air Purifying Respirator (APR) with a CBRN Canister,
or a Chemical Warfare Agents (CWA) tested full facepiece APR with a combination organic vapor/acid gas/particulate canister.

Skin Protection: An encapsulating Level A type suit which provides skin vapor protection constructed of butyl rubber or layered impervious clothing which has received material and construction testing against specific CBRN agents by the manufacturer, the government or a third party testing agency using an accepted protocol. The NFPA 1991 Standard on Vapor-Protective Ensembles for Hazardous Materials Emergencies and the NFPA 1994 Standard on protective Ensembles for Chemical/Biological Terrorism Incidents require mandatory testing against chemical warfare agents.

Skin Protection: An encapsulating Level A type suit which provides skin vapor protection. A butyl rubber or layered impervious
clothing which has received material and construction testing against specific CBRN agents by the manufacturer, the government or a third party testing agency using an accepted
protocol. The NFPA 1991 Standard on Vapor-Protective Ensembles for Hazardous Materials Emergencies requires mandatory testing against chemical warfare agents.

j) Veterans at Risk: The Health Effects of Mustard Gas and Lewisite. National Academy of Sciences, Institute of Medicine, Committee to Survey the Health
Effects of Mustard Gas and Lewisite. National Academy Press, Washington, DC., (1993).

Specific Hazard Information

Related Online Resources

NOTICE

This product is not a standard or regulation, and it has no effect on employers' legal obligations. The guidance is advisory in nature, informational in content, and is intended only as technical assistance to employers in providing a safe and healthful workplace during emergency response operations. This document does not enhance or diminish any existing obligations under the OSH Act. The information in this document is interim guidance only. It is anticipated that NIOSH CBRN approval for all classes of respirators will be available in the near future. This guidance will change at the time NIOSH CBRN certification standards are available for all respirator classes. OSHA also may update this guidance as additional information becomes available in the future.

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